CN116859521B - Grating coupler and preparation method thereof - Google Patents

Abstract

The application provides a grating coupler and a preparation method thereof. The grating coupler comprises a silicon-based substrate, a first reflecting layer formed on the silicon-based substrate, a lower buried layer formed on the first reflecting layer, a waveguide layer formed on the lower buried layer, an upper cladding layer formed on the waveguide layer, and a second reflecting layer formed on the upper cladding layer, wherein the waveguide layer comprises a plurality of two-dimensional gratings, and the two-dimensional gratings are arranged along the direction of a light path propagation path. And part of the incident light entering from one two-dimensional grating passes through the two-dimensional grating along the direction of the light path propagation path and then enters the next two-dimensional grating under the reflection action of the first reflecting layer and the second reflecting layer. The polarization-insensitive optical fiber can simultaneously give consideration to insensitivity to polarization and high coupling efficiency.

Description

Grating coupler and preparation method thereof

Technical field

The present application relates to the technical field of silicon-based optoelectronic chips, and in particular to a grating coupler and a preparation method thereof.

Background technique

From the PC+ (Personal Computer, personal computer) Internet era to the mobile+social media era, to the future AI+ (Artificial Intelligence, artificial intelligence) big data era, growing and diversified system requirements are driving the development of many technologies. In the context of the slowdown of Moore's Law, photonic chips used in photon computing are proposed to replace traditional electronic chips. Photonic chips have the advantages of low loss and high bandwidth. Limited by equipment and manufacturing processes, it has become increasingly difficult to directly package the optical ports and electrical ports on the chip. An external laser source must be used and coupled indirectly or directly with a PIC (Photonic Integrated Circuit). Coupling methods include grating coupling, edge coupling, evanescent coupling, etc. Grating couplers are widely used because of their freedom in on-chip design positions and mature technology. However, the coupling loss of a simple-structured grating coupler is high. In order to reduce the coupling loss, some people have designed novel and complex grating structures, and some have designed underlying reflective metal. These methods can reduce the coupling loss.

Contents of the invention

The purpose of this application is to provide a grating coupler and a preparation method thereof, which can take into account both insensitivity to polarization and high coupling efficiency.

One aspect of the present application provides a grating coupler. The grating coupler includes a silicon-based substrate, a first reflective layer formed on the silicon-based substrate, a buried layer formed on the first reflective layer, and a waveguide formed on the buried layer. layer, an upper cladding layer formed on the waveguide layer, and a second reflective layer formed on the upper cladding layer. The waveguide layer includes a plurality of two-dimensional gratings, and the plurality of two-dimensional gratings are along the optical path. Propagation path direction settings. Wherein, along the direction of the optical path propagation path, part of the incident light entering from a two-dimensional grating will be reflected by the first reflective layer and the second reflective layer after passing through the two-dimensional grating. Proceed to the next 2D raster.

Further, the waveguide layer further includes a plurality of first waveguides and a plurality of second waveguides, the plurality of first waveguides are located on the first side of the plurality of two-dimensional gratings, and the plurality of second waveguides are located on the first side of the two-dimensional gratings. A portion of the incident light entering from one two-dimensional grating is diffracted from a second side of the plurality of two-dimensional gratings opposite the first side, wherein light of a transverse electric field mode in the incident light is coupled to The first waveguide located on the first side, the transverse magnetic field mode light in the incident light is coupled to the second waveguide located on the second side.

Further, the waveguide layer further includes a first beam combiner and a second beam combiner. The first beam combiner is used to combine the light in the plurality of first waveguides. The second beam combiner The device is used to combine the light in the plurality of second waveguides.

Further, the waveguide layer further includes a first mode spot converter and a second mode spot converter, and the first side of each two-dimensional grating is coupled to the third mode spot converter through the first mode spot converter. A waveguide, the second side of each of the two-dimensional gratings is coupled to the second waveguide through the second mode spot converter.

Further, the second reflective layer is shorter than the first reflective layer to leave space for coupling optical fibers, and the materials of the first reflective layer and the second reflective layer include gold.

Further, the incident angle of the incident light is greater than 30 degrees.

Further, the two-dimensional grating includes a hole array, the grating area of the two-dimensional grating is square, and the right-angled sides of the square are arranged at an angle of 45 degrees to the direction of the light propagation path.

Further, the buried layer includes a lower silicon dioxide layer, the upper cladding layer includes an upper silicon dioxide layer, and the material of the plurality of two-dimensional gratings includes silicon nitride.

Another aspect of the present application provides a method of manufacturing a grating coupler. The preparation method includes: forming a first reflective layer on the silicon-based substrate; forming a buried layer on the first reflective layer; forming a waveguide layer on the buried layer, which includes: A plurality of two-dimensional gratings are arranged on the lower buried layer along the direction of the optical path propagation path; an upper cladding layer is formed on the waveguide layer; and a second reflective layer is formed on the upper cladding layer. Wherein, along the direction of the optical path propagation path, part of the incident light entering from a two-dimensional grating will be reflected by the first reflective layer and the second reflective layer after passing through the two-dimensional grating. Proceed to the next 2D raster.

Further, forming a waveguide layer on the buried layer further includes: arranging a plurality of first waveguides on the first side of the two-dimensional gratings on the buried layer; and A plurality of second waveguides are provided on the layer on a second side of the plurality of two-dimensional gratings opposite to the first side, wherein part of the incident light entering from one two-dimensional grating is diffracted, wherein, the A transverse electric field mode of the incident light is coupled to the first waveguide on the first side, and a transverse magnetic field mode of the incident light is coupled to the second waveguide on the second side. waveguide.

Further, forming a waveguide layer on the buried layer further includes: providing a first beam combiner on the buried layer for combining the light in the plurality of first waveguides; and A second beam combiner for combining the light in the plurality of second waveguides is provided on the buried layer.

Further, the preparation method also includes: predetermining a single two-dimensional grating coupler through simulation; and simulating and determining the optimal operating parameters of a single two-dimensional grating based on the single two-dimensional grating coupler, wherein, according to the single two-dimensional grating coupler, The optimal operating parameters of the two-dimensional grating form a plurality of the two-dimensional gratings on the buried layer along the direction of the light path propagation path.

Further, the single two-dimensional grating coupler has a two-dimensional grating with a periodically arranged hole array, and the simulation to determine the optimal operating parameters of the single two-dimensional grating based on the single two-dimensional grating coupler includes: establishing the A model of a single two-dimensional grating coupler and optical fiber coupling; a mode light source is set at the optical fiber for emitting mode light with a predetermined input power; power monitoring is set on adjacent two sides of the single two-dimensional grating coupler. The detector is used to monitor the output power of the mode light on two adjacent sides respectively; and with the output power of the mode light on the two adjacent sides as the optimization target, the simulation optimization method is used to optimize the inner hole in the two-dimensional grating. The radius and period are continuously and iteratively optimized to obtain the best working parameters of a single two-dimensional grating.

Further, the single two-dimensional grating coupler is designed and simulated in finite difference time domain simulation software.

Furthermore, the particle swarm simulation optimization method is used to continuously and iteratively optimize the radius and period of the inner hole in the two-dimensional grating.

The grating coupler of the embodiment of the present application and the grating coupler manufactured by the preparation method of the embodiment of the present application can at least achieve the following beneficial technical effects:

(1) This application uses a two-dimensional grating. The two-dimensional grating is insensitive to the polarization of the incident light. The incident light can be introduced to the opposite sides of multiple two-dimensional gratings respectively, thereby achieving the polarization insensitivity of the incident light.

(2) In this application, a first reflective layer and a second reflective layer are respectively added below the buried layer and above the upper cladding layer, and multiple cascaded two-dimensional gratings are arranged in the waveguide layer along the direction of the optical path propagation path. The grating area is lengthened, so that the incident light can be reflected multiple times between the first reflective layer and the second reflective layer and pass through the grating areas of multiple cascaded two-dimensional gratings, thereby increasing the overall coupling efficiency.

Description of the drawings

Figure 1 is an overall top view of a grating coupler according to an embodiment of the present application.

Figure 2 is an overall side view of a grating coupler according to an embodiment of the present application.

Figure 3 is a top view of a single two-dimensional grating coupler according to an embodiment of the present application.

Figure 4 is a schematic side view of a single two-dimensional grating coupler in simulation according to an embodiment of the present application.

Figure 5 is a flow chart of a method for manufacturing a grating coupler according to an embodiment of the present application.

FIG. 6 is a specific process flow chart of a method for manufacturing a grating coupler according to an embodiment of the present application.

Detailed ways

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings refer to the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of means consistent with aspects of the application as detailed in the appended claims.

The terminology used in the embodiments of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application. Unless otherwise defined, the technical terms or scientific terms used in the embodiments of this application should have the usual meanings understood by those with ordinary skills in the field to which this application belongs. As used in this specification and the appended claims, the singular forms "a," "the" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

The embodiment of the present application provides a grating coupler 10. FIG. 1 shows an overall top view of the grating coupler 10 according to one embodiment of the present application, and FIG. 2 shows an overall side view of the grating coupler 10 according to one embodiment of the present application. As shown in FIGS. 1 and 2 , a grating coupler 10 according to an embodiment of the present application includes a silicon-based substrate 11 , a first reflective layer 12 formed on the silicon-based substrate 11 , and a first reflective layer 12 formed on the first reflective layer 12 . The lower buried layer 13 , the waveguide layer 14 formed on the lower buried layer 13 , the upper cladding layer 15 formed on the waveguide layer 14 , and the second reflective layer 16 formed on the upper cladding layer 15 .

The waveguide layer 14 includes a plurality of two-dimensional gratings 141, and the plurality of two-dimensional gratings 141 are arranged along the direction of the optical propagation path. Among them, along the direction of the optical path propagation path, part of the incident light entering from a two-dimensional grating 141 passes through the two-dimensional grating 141 and enters under the reflection of the first reflective layer 12 and the second reflective layer 16. Next 2D grating141.

As shown in FIG. 1 , in some embodiments, the waveguide layer 14 further includes a plurality of first waveguides 142 and a plurality of second waveguides 143 . The plurality of first waveguides 142 are located on the first side of the plurality of two-dimensional gratings 141 , and the plurality of second waveguides 143 are located on the second side of the plurality of two-dimensional gratings 141 that is opposite to the first side. Part of the light in the incident light entering from a two-dimensional grating 141 is diffracted, wherein the transverse electric field (TE, Transverse Electric) mode light in the incident light is coupled to the first waveguide 142 located on the first side, and the light in the incident light is Transverse Magnetic (TM) mode light is coupled to the second waveguide 143 located on the second side. In the embodiment shown in FIG. 1 , the first side of the plurality of two-dimensional gratings 141 may be, for example, the upper side shown in FIG. 1 , and the second side may be the lower side shown in FIG. 1 . Of course, in other embodiments, the first side of the plurality of two-dimensional gratings 141 may also be the lower side as shown in FIG. 1 , and the second side may be the upper side as shown in FIG. 1 , and this application is not limited thereto.

In some embodiments, the waveguide layer 14 may also include a first beam combiner 144 and a second beam combiner 145 . The first beam combiner 144 may be used to combine the light in the plurality of first waveguides 142 , and the second beam combiner 145 may be used to combine the light in the plurality of second waveguides 143 .

In some embodiments, the waveguide layer 14 further includes a first mode taper 146 and a second mode taper 147 . The first side of each two-dimensional grating 141 is coupled to the first waveguide 142 through the first mode spot converter 146, and the second side of each two-dimensional grating 141 is coupled to the second waveguide 143 through the second mode spot converter 147. The first mode spot converter 146 and the second mode spot converter 147 are used to transition single-mode light from a wider waveguide to a narrower waveguide.

The lower buried layer 13 may include, for example, a lower silicon dioxide (SiO ₂ ) layer, and the upper cladding layer 15 may include, for example, an upper silicon dioxide (SiO ₂ ) layer.

In one embodiment, the material of the first reflective layer 12 and the second reflective layer 16 may be gold (Au). Of course, the material of the first reflective layer 12 and the second reflective layer 16 of the present application is not limited to gold. In other embodiments, the first reflective layer 12 and the second reflective layer 16 may also be made of highly reflective materials such as aluminum (Al). As shown in FIG. 2 , the second reflective layer 16 is shorter than the first reflective layer 12 to leave space for the coupling optical fiber 20 .

In one embodiment, the material of the plurality of two-dimensional gratings 141 can be silicon nitride, which can make the process simpler. Of course, in other embodiments, the material of the plurality of two-dimensional gratings 141 can also be silicon carbide.

1 and 2 , the light incident through the optical fiber 20 is diffracted after passing through the first two-dimensional grating 141 , in which the TE mode light and the TM mode light in the incident light are respectively coupled into the two-dimensional grating 141 The first waveguide 142 and the second waveguide 143 are on opposite sides. Due to the existence of the first reflective layer 12 and the second reflective layer 16, the first reflective layer 12 and the second reflective layer 16 have extremely high reflectivity for light within a certain wavelength range. Therefore, from the first two-dimensional grating 141 The light that escapes will continue to reflect between the first reflective layer 12 and the second reflective layer 16. After multiple reflections, it will enter the second two-dimensional grating 141, and then pass through the second two-dimensional grating 141. Then diffraction occurs and is coupled to the first waveguide 142 and the second waveguide 143 on opposite sides of the two-dimensional grating 141. Then, part of the light incident on the second two-dimensional grating 141 passes through the second two-dimensional grating. After 141, it will be introduced into the third two-dimensional grating 141 under the reflection of the first reflective layer 12 and the second reflective layer 16. In this way, it will be diffracted and exported in multiple two-dimensional gratings 141 until it passes through the last one. Two-dimensional grating141. The diffracted light generated by passing through the two-dimensional grating 141 each time will be derived from the first waveguide 142 and the second waveguide 143. Finally, the plurality of two-dimensional gratings 141 are coupled by the first beam combiner 144 and the second beam combiner 145 respectively. The light in the first waveguide 142 and the second waveguide 143 is combined together. As a result, very high coupling efficiency can be achieved and it is polarization-insensitive to incident light.

In some embodiments, each two-dimensional grating 141 in the grating coupler 10 of the present application may include a hole array. Figure 3 reveals a top view of a single two-dimensional grating device according to an embodiment of the present application. As shown in FIG. 3 , the shape of the inner holes in the hole array included in the two-dimensional grating 141 may be circular or rectangular. Preferably round to facilitate processing. In some embodiments, the grating areas of the two-dimensional grating 141 are square. As shown in FIG. 1 , preferably, the square right-angled sides of the plurality of two-dimensional gratings 141 are arranged at an angle of 45 degrees to the direction of the light propagation path, so that the TE mode light and the TM mode light can be better separated.

As shown in FIG. 2 , in some embodiments, the incident angle θ of the incident light is greater than 30 degrees, so that the light reflected back from the first reflective layer 12 for the first time can be incident on the second reflective layer 16 .

In order to design the grating coupler 10 having the first reflective layer 12 and the second reflective layer 16 and having multiple two-dimensional gratings 141 cascaded in the embodiment of the present application, a single two-dimensional grating coupler can be designed and simulated in advance. Figure 4 reveals a schematic side view of a single two-dimensional grating coupler in simulation according to an embodiment of the present application. As shown in FIG. 4 , a single two-dimensional grating coupler can be pre-designed and simulated in the simulation software, and the optimal operating parameters of the single two-dimensional grating 141 can be simulated and determined based on the single two-dimensional grating coupler. Then, multiple two-dimensional gratings 141 in the direction of the optical propagation path in the grating coupler 10 of the present application can be designed according to the optimal operating parameters of the single two-dimensional grating 141 .

For example, the single two-dimensional grating coupler can be designed and simulated in Finite-DifferenceTime-Domain (FDTD) simulation software. The single two-dimensional grating coupler has a two-dimensional grating 141 with a grating area size of 12um (micron) × 12um square area, so that it can be suitable for mode matching with the standard single-mode optical fiber 20 . The two-dimensional grating 141 is a periodically arranged hole array. The thickness of the first reflective layer 12 and the second reflective layer 16 is 100 nm (nanometer), and the material is gold (Au). The lower buried layer 13 is the lower silicon dioxide layer, with a thickness of 3um, and the upper cladding layer 15 is the upper silicon dioxide layer, with a thickness of 3um (micron). The diameter of the optical fiber cladding 21 in the optical fiber 20 is 50um, and the diameter of the optical fiber core 22 is 9um.

A model of coupling between the single two-dimensional grating coupler and the optical fiber 20 is established. After the construction is completed, a mode light source (not shown) is added to the optical fiber 20 and a fundamental mode is selected to emit mode light with a predetermined input power. Among them, the optical fiber 20 is incident obliquely into the two-dimensional grating 141 at a certain angle. For example, the incident light in the optical fiber 20 is incident at an angle of 30°. After passing through the upper silica layer, it enters the two-dimensional grating 141 and undergoes diffraction, and enters into Figure 3 respectively. The two-dimensional grating 141 is shown with the first mode spot converter 146 and the second mode spot converter 147 on adjacent sides.

As shown in Figure 3, power monitors 30 are respectively provided on both adjacent sides of the single two-dimensional grating coupler. The adjacent two sides of the single two-dimensional grating coupler are used as monitoring ports to monitor these locations respectively. The mode field distribution of the waveguide and the output power of the mode light. The software's built-in optimization function can be used to take the output power of the adjacent two side mode lights as the optimization target, and the radius and period of the inner hole in the two-dimensional grating 141 can be continuously and iteratively optimized through the simulation optimization method. For example, optimization can be based on the particle swarm simulation optimization method to continuously iterate and calculate the output power of the mode light at the monitoring port, and select the output power of the mode light as the optimization target. Within a certain number of iterations, the waveguide at the monitoring port can have the maximum The output power of the mode light. The optimal operating parameters of the single two-dimensional grating 141 are the radius and period of the inner hole of the two-dimensional grating 141 corresponding to the maximum output power of the mode light.

After the optimal operating parameters of a single two-dimensional grating 141 are obtained through the above optimization, multiple two-dimensional gratings 141 can be arranged in the direction of the optical path propagation path using the arrangement shown in FIG. 2 .

The grating coupler 10 in the embodiment of the present application adopts a two-dimensional grating 141. The two-dimensional grating 141 is not sensitive to the polarization of the incident light and can guide the incident light to the opposite sides of the multiple two-dimensional gratings 141, thereby achieving the incident light. Polarization insensitivity of light.

In addition, the grating coupler 10 in the embodiment of the present application adds the first reflective layer 12 and the second reflective layer 16 respectively below the lower buried layer 13 and above the upper cladding layer 15, and propagates along the optical path in the waveguide layer 14. Multiple cascaded two-dimensional gratings 141 are arranged in the direction to lengthen the grating area, so that the incident light can be reflected multiple times between the first reflective layer 12 and the second reflective layer 16 and pass through the multiple cascaded two-dimensional gratings. 141 grating area increases the overall coupling efficiency.

Therefore, the grating coupler 10 of the embodiment of the present application can achieve both insensitivity to polarization and high coupling efficiency.

The embodiment of the present application also provides a method of manufacturing the grating coupler 10 . FIG. 5 reveals a flow chart of a method for manufacturing a grating coupler 10 according to an embodiment of the present application, and FIG. 6 shows a specific process flow chart of a method for manufacturing the grating coupler 10 according to an embodiment of the present application. Referring to FIGS. 5 and 6 , the method for manufacturing the grating coupler 10 according to one embodiment of the present application may adopt a thin film growth process, which may include steps S1 to S5.

In step S1 , the first reflective layer 12 is formed on the silicon-based substrate 11 .

In step S2 , a buried layer 13 is formed on the first reflective layer 12 .

In step S3 , the waveguide layer 14 is formed on the underlying buried layer 13 .

Step S3 may further include step S31. In step S31, a plurality of two-dimensional gratings 141 are provided on the underlying buried layer 13 along the direction of the optical propagation path.

In some embodiments, step S3 may further include step S32. Referring to FIG. 1 , in step S32 , a plurality of first waveguides 142 are provided on the first side of the plurality of two-dimensional gratings 141 on the underlying buried layer 13 ; A plurality of second waveguides 143 are provided on the second side opposite to one side. As shown in FIG. 2 , in which part of the incident light entering from a two-dimensional grating 141 is diffracted, in which the transverse electric field mode light in the incident light is coupled to the first waveguide 142 located on the first side, the incident light The light in the transverse magnetic field mode is coupled to the second waveguide 143 located on the second side.

In some embodiments, step S3 may further include step S33. In step S33, a first beam combiner 144 for combining the light in the plurality of first waveguides 142 is provided on the underlying buried layer 13; and a first beam combiner 144 for combining the plurality of second waveguides 143 is provided on the underlying buried layer 13. The second beam combiner 145 combines the light.

In step S4, the upper cladding layer 15 is formed on the waveguide layer 14.

In step S5, the second reflective layer 16 is formed on the upper cladding layer 15. The second reflective layer 16 should be shorter than the first reflective layer 12 to leave space for the optical fiber 20 for coupling.

Referring to FIG. 2 , along the direction of the light propagation path, part of the incident light from a two-dimensional grating 141 will pass through the two-dimensional grating 141 and will be reflected between the first reflective layer 12 and the second reflective layer 16 . It enters the next two-dimensional grating 141 under reflection.

In some embodiments, the method for preparing the grating coupler 10 of the present application may further include step S6 and step S7.

In step S6, a single two-dimensional grating coupler is predetermined through simulation.

In one embodiment, a single two-dimensional grating coupler can be designed and simulated in finite difference time domain simulation software. The single two-dimensional grating coupler has a two-dimensional grating 141 of a periodically arranged hole array, as shown in FIG. 3 .

In step S7, the optimal operating parameters of the single two-dimensional grating 141 are determined through simulation based on the single two-dimensional grating coupler.

After the optimal operating parameters of the single two-dimensional grating 141 are determined, in step S31 , multiple two-dimensional gratings can be formed on the underlying layer 13 along the direction of the optical path according to the optimal operating parameters of the single two-dimensional grating 141 . Raster141.

In some embodiments, step S7 may further include steps S71 to S74. In step S71, a coupling model of the single two-dimensional grating coupler and the optical fiber 20 is established. In step S72 , a pattern light source (not shown) is set at the optical fiber 20 for emitting pattern light with a predetermined input power. In step S73, power monitors 30 (as shown in FIG. 3) are respectively provided on two adjacent sides of the single two-dimensional grating coupler for monitoring the output power of the mode light on the adjacent two sides. In step S74, with the output power of the mode light on adjacent two sides as the optimization target, the radius and period of the inner hole in the two-dimensional grating 141 are continuously and iteratively optimized through the simulation optimization method to obtain the value of the single two-dimensional grating 141. optimal working parameters. In one embodiment, the radius and period of the inner hole in the two-dimensional grating 141 can be continuously and iteratively optimized through a particle swarm simulation optimization method.

The grating coupler 10 manufactured by the above preparation method of the present application can achieve both insensitivity to polarization and high coupling efficiency.

The grating coupler and its preparation method provided in the embodiments of the present application have been introduced in detail above. This article uses specific examples to illustrate the grating coupler and its preparation method according to the embodiments of the present application. The description of the above embodiments is only used to help understand the core idea of the present application and is not intended to limit the present application. It should be pointed out that for those of ordinary skill in the art, several improvements and modifications can be made to the present application without departing from the spirit and principles of the present application, and these improvements and modifications should also fall into the appendix of the present application. within the scope of protection of the claims.

Claims (15)

1. A grating coupler, characterized by: the light source device comprises a silicon-based substrate, a first reflecting layer formed on the silicon-based substrate, a lower buried layer formed on the first reflecting layer, a waveguide layer formed on the lower buried layer, an upper cladding layer formed on the waveguide layer and a second reflecting layer formed on the upper cladding layer, wherein the waveguide layer comprises a plurality of two-dimensional gratings, the two-dimensional gratings are arranged along the direction of a light path propagation path, and part of incident light entering from one two-dimensional grating enters the next two-dimensional grating under the reflecting action of the first reflecting layer and the second reflecting layer after passing through the two-dimensional grating along the direction of the light path propagation path.

2. The grating coupler of claim 1, wherein: the waveguide layer further includes a plurality of first waveguides located on a first side of the plurality of two-dimensional gratings and a plurality of second waveguides located on a second side of the plurality of two-dimensional gratings opposite the first side, a portion of light from incident light entering from one two-dimensional grating being diffracted, wherein light of a transverse electric field mode in the incident light is coupled to the first waveguides located on the first side, and light of a transverse magnetic field mode in the incident light is coupled to the second waveguides located on the second side.

3. The grating coupler of claim 2, wherein: the waveguide layer further includes a first beam combiner for combining light in the plurality of first waveguides and a second beam combiner for combining light in the plurality of second waveguides.

4. The grating coupler of claim 2, wherein: the waveguide layer further includes a first mode spot-changer and a second mode spot-changer, the first side of each of the two-dimensional gratings being coupled to the first waveguide by the first mode spot-changer, the second side of each of the two-dimensional gratings being coupled to the second waveguide by the second mode spot-changer.

5. The grating coupler of claim 1, wherein: the second reflective layer is shorter than the first reflective layer to allow a location for coupling an optical fiber, and the materials of the first and second reflective layers include gold.

6. The grating coupler of claim 1, wherein: the incident angle of the incident light is greater than 30 degrees.

7. The grating coupler of claim 1, wherein: the two-dimensional grating comprises a hole-shaped array, the grating area of the two-dimensional grating is square, and the right-angle side of the square is inclined to the direction of the light path propagation path by 45 degrees.

8. The grating coupler of claim 1, wherein: the lower buried layer comprises a lower silicon dioxide layer, the upper cladding layer comprises an upper silicon dioxide layer, and the materials of the two-dimensional gratings comprise silicon nitride.

9. A preparation method of a grating coupler is characterized by comprising the following steps: comprising the following steps:

forming a first reflective layer on a silicon-based substrate;

forming a lower buried layer on the first reflective layer;

forming a waveguide layer on the lower buried layer, comprising:

a plurality of two-dimensional gratings are arranged on the lower buried layer along the direction of the light path propagation path;

forming an upper cladding layer on the waveguide layer; and

a second reflective layer is formed on the upper cladding layer,

and part of the incident light entering from one two-dimensional grating passes through the two-dimensional grating along the direction of the light path propagation path and then enters the next two-dimensional grating under the reflection action of the first reflecting layer and the second reflecting layer.

10. The method of preparing as claimed in claim 9, wherein: the forming a waveguide layer on the lower buried layer further includes:

a plurality of first waveguides are arranged on the first side of the two-dimensional gratings on the lower buried layer; and

A plurality of second waveguides are disposed on a second side of the buried layer opposite the first side of the plurality of two-dimensional gratings,

wherein part of the light of the incident light entering from one two-dimensional grating is diffracted, wherein light of a transverse electric field mode of the incident light is coupled to the first waveguide at the first side and light of a transverse magnetic field mode of the incident light is coupled to the second waveguide at the second side.

11. The method of manufacturing as claimed in claim 10, wherein: the forming a waveguide layer on the lower buried layer further includes:

a first beam combiner for combining the light in the plurality of first waveguides is arranged on the lower buried layer; and

And a second beam combiner for combining the light in the plurality of second waveguides is arranged on the lower buried layer.

12. The method of preparing as claimed in claim 9, wherein: further comprises:

a single two-dimensional grating coupler is predetermined through simulation; and

The optimal operating parameters of a single two-dimensional grating are determined based on the simulation of the single two-dimensional grating coupler,

wherein a plurality of the two-dimensional gratings are formed on the buried layer along the optical path propagation path direction according to the optimal operation parameters of the single two-dimensional grating.

13. The method of manufacturing as claimed in claim 12, wherein: the single two-dimensional grating coupler has a two-dimensional grating with a periodically arranged hole array, and the determining, based on the single two-dimensional grating coupler, the optimal operating parameters of the single two-dimensional grating includes:

establishing a model of the single two-dimensional grating coupler and the optical fiber coupling;

providing a mode light source at the optical fiber for emitting mode light having a predetermined input power;

respectively arranging power monitors on two adjacent sides of the single two-dimensional grating coupler, wherein the power monitors are respectively used for monitoring the output power of the mode light of the two adjacent sides; and

And taking the output power of the mode light on two adjacent sides as an optimization target, and continuously performing iterative optimization on the radius and the period of the inner hole in the two-dimensional grating by using a simulation optimization method so as to obtain the optimal working parameters of the single two-dimensional grating.

14. The method of manufacturing as claimed in claim 13, wherein: and designing and simulating the single two-dimensional grating coupler in time domain finite difference method simulation software.

15. The method of manufacturing as claimed in claim 13, wherein: and continuously performing iterative optimization on the radius and the period of the inner hole in the two-dimensional grating by a particle swarm simulation optimization method.